Baseball and softball players continually search for better bats to improve their hitting performance. Bat performance is generally based upon length, weight, moment of inertia (MOI) and impact response during contact with the ball. Manufacturers have made attempts to improve the impact response during contact with the ball using a variety of material construction. Unfortunately, each of these prior attempts has various shortcomings.
As manufacturers have improved bats, various regulatory bodies and administrators of organized baseball and softball games have placed restrictions on bat performance and configuration. In order to limit the maximum response to the bat, manufacturers have traditionally modified their designs to dampen the response to all impacts. In other words, these designs reduce the responsiveness of the bat at both low impact speeds as well as high impact speeds. Typically this is done by adding material to the thickness of the barrel portion of the bat to increase the hoop of stiffness. This approach hinders the hitting performance of less skilled players in an effort to control the maximum rebound speed generated by the best players.
Bat rebound performance is generally maximized at a narrow width of the barrel commonly referred to as the sweet spot. The prior art includes several attempts to produce a bat with reduced performance at the sweet spot. The intent of these designs has been to level the impact response along the width of the barrel, effectively widening the perceived sweet spot. These attempts have several shortfalls. For example, U.S. Pat. No. 6,949,038, issued to Fritzke, discloses increasing in the wall thickness of the bat near the sweet spot. This is accomplished, for example, by including an insert 22, as illustrated in FIG. 4, having first and second tubular wall transition regions 36 and 38, as well as an intermediate tubular region 40, having an increased thickness. Additionally, as illustrated with respect to FIG. 7, an intermediate tubular region 140 provided on the outside surface of the bat would also have an increased thickness. As can be appreciated, the added thickness of the insert or the outer portion of the bat would add additional weight and create stress concentrations at each end of the thicker regions.
Consequently, there is a need to provide an improved bat which would meet regulation standards for maximum barrel response with less dampening at slower speed impacts.
Additionally, there is a need to produce a bat having a more consistent impact response along the length of the barrel than conventional bats without the increased weight or the creation of stress concentrations, as described in prior art references.
Baseball bats are generally constructed having a barrel portion, a tapered portion and a handle portion. Recently, several U.S. patents have illustrated non-wood bats provided with a foam in the interior of the bat filling at least a portion of the barrel as well as perhaps a portion of the tapered portion. For example, U.S. Pat. Nos. 6,248,032, 6,334,824 and 6,432,007, issued to Filice et al describe an aluminum shell bat including a foam filler 30 comprising a syntactic foam which substantially fills the interior of the bat shell 10 in the hitting area by filling the entire barrel of the bat as well as a portion of the tapered area. It is important to note that the foam filler 30 consists of only a single density material.
U.S. Pat. Nos. 5,458,330 and 5,533,723 both issued to Baum describe a composite baseball bat provided with a core in the barrel section. This baseball bat includes a layer of wood-like veneer covering a layer of fiber reinforced resin. FIGS. 12 and 13 illustrate a bat having a core with a central cavity. As discussed in column 4, lines 18-30 of both patents, a core 28 is provided formed from a resilient urethane foam. It is noted that this core 28 extends around a plug 31 in the barrel portion of the bat as well as extending throughout the handle portion. As further described in column 5, lines 20-51 of the '723 patent, the plug 31 is provided within the central cavity formed of a different and generally less dense material than the core 28. Since the plug material 31 is less dense than the material of the core, the plug 31 would be more compressible than the core 28.
U.S. Pat. No. 3,810,098 issued to Gildemeister discusses a metallic baseball bat including a hollow tube having a rigid urethane foam core 20 as well as a plug 15a comprised of a heavier foam than the core 20. It is noted that the plug 15a does not surround the rigid urethane foam but is provided adjacent to the end cap portion of the bat.
U.S. Pat. No. 5,964,673 issued to MacKay, Jr. describes a hollow metallic bat containing one or more resilient sponge-like balls 26. A hardenable material 28, such as urethane or the like is provided around a portion of one of the balls as shown in FIG. 4 or would completely surround a sponge ball as illustrated with respect to FIG. 5.
However, it has been found that the aforementioned designs would produce a bat in which the hitting performance of the less skilled players might be compromised in the effort to control the maximum rebound speed generated by the best players.
Consequently, a need has arisen in which the placement and type of foam materials particularly within the barrel portion of the bat would be crucial to elevating the performance of lesser players without hindering the performance of the better players.